Monitoring of water stress in wheat using multispectral indices derived from Landsat-TM     

Nitika Dangwal  N.R. Patel  Mamta Kumari  S.K. Saha 《国际地球制图》2016,31(6):682-693

Detection of crop water stress is crucial for efficient irrigation water management. Potential of Satellite data to provide spatial and temporal dynamics of crop growth conditions makes it possible to monitor crop water stress at regional level. This study was conducted in parts of western Uttar Pradesh and Haryana. Multi-temporal Landsat data were used for detecting wheat crop water stress using vegetation indices (VIs), viz. vegetation water stress index (VWSI) and land surface wetness index water stress factor (Ws_LSWI). The estimated water stress from satellite data-based VIs was validated by water stress factor (Ws) derived from flux-tower data. The study observed Ws_LSWI to be better index for water stress detection. The results indicated that Ws_LSWI was superior over other index showing RMSE = 0.12, R² = 0.65, whereas VWSI showed overestimated values with mean RD 4%.  相似文献   

Deciphering As and Cu cycling in sediment pore waters in a large marina (Port Camargue,southern France) using a multi-tracer (Fe,Mn, U,Mo) approach     

《Applied Geochemistry》2016

The sediments of the Port Camargue marina (South of France) are highly polluted by Cu and As (Briant et al., 2013). The dynamics of these pollutants in pore waters was investigated using redox tracers (sulfides, Fe, Mn, U, Mo) to better constrain the redox conditions.In summer, pore water profiles showed a steep redox gradient in the top 24 cm with the reduction of Fe and Mn oxy-hydroxides at the sediment water interface (SWI) and of sulfate immediately below. Below a depth of 24 cm, the Fe, Mn, Mo and U profiles in pore waters reflected Fe and Mn reducing conditions and, unlike in the overlying levels, sulfidic conditions were not observed. This unusual redox zonation was attributed to the occurrence of two distinct sediment layers: an upper layer comprising muddy organic-rich sediments underlain by a layer of relatively sandy and organic-poor sediments. The sandy sediments were in place before the building of the marina, whereas the muddy layer was deposited later. In the muddy layer, large quantities of Fe and Mo were removed in summer linked to the formation of insoluble sulfide phases. Mn, which can adsorb on Fe-sulfides or precipitate with carbonates, was also removed from pore waters. Uranium was removed probably through reduction and adsorption onto particles. In winter, in the absence of detectable pore water sulfides, removal of Mo was moderate compared to summer.Cu was released into solution at the sediment water interface but was efficiently trapped by the muddy layer, probably by precipitation with sulfides. Due to efficient trapping, today the Cu sediment profile reflects the increase in its use as a biocide in antifouling paints over the last 40 years.In the sandy layer, Fe, Mn, Mo and As were released into solution and diffused toward the top of the profile. They precipitated at the boundary between the muddy and sandy layers. This precipitation accounts for the high (75 μg g⁻¹) As concentrations measured in the sediments at a depth of 24 cm.  相似文献   

Reactive transport impacts on recovered freshwater quality during multiple partially penetrating wells (MPPW-)ASR in a brackish heterogeneous aquifer     

《Applied Geochemistry》2016

The use of multiple partially penetrating wells (MPPW) during aquifer storage and recovery (ASR) in brackish aquifers can significantly improve the recovery efficiency (RE) of unmixed injected water. The water quality changes by reactive transport processes in a field MPPW-ASR system and their impact on RE were analyzed. The oxic freshwater injected in the deepest of four wells was continuously enriched with sodium (Na⁺) and other dominant cations from the brackish groundwater due to cation exchange by repeating cycles of ‘freshening’. During recovery periods, the breakthrough of Na⁺ was retarded in the deeper and central parts of the aquifer by ‘salinization’. Cation exchange can therefore either increase or decrease the RE of MPPW-ASR compared to the RE based on conservative Cl⁻, depending on the maximum limits set for Na⁺, the aquifer’s cation exchange capacity, and the native groundwater and injected water composition. Dissolution of Fe and Mn-containing carbonates was stimulated by acidifying oxidation reactions, involving adsorbed Fe²⁺ and Mn²⁺ and pyrite in the pyrite-rich deeper aquifer sections. Fe²⁺ and Mn²⁺ remained mobile in anoxic water upon approaching the recovery proximal zone, where Fe²⁺ precipitated via MnO₂ reduction, resulting in a dominating Mn²⁺ contamination. Recovery of Mn²⁺ and Fe²⁺ was counteracted by frequent injections of oxygen-rich water via the recovering well to form Fe and Mn-precipitates and increase sorption. The MPPW-ASR strategy exposes a much larger part of the injected water to the deeper geochemical units first, which may therefore control the mobilization of undesired elements during MPPW-ASR, rather than the average geochemical composition of the target aquifer.  相似文献   

青藏高原地区云水时空变化特征及其与降水的联系   总被引：4，自引：1，他引：3  

伯玥  王艺  李嘉敏  王澄海 《冰川冻土》2016,(6):1679-1690

利用1984-2009年ISCCP的云量、云光学厚度(COT)、云水路径(CWP)资料,分析了青藏高原云水的分布特征、变化趋势,及其与夏秋季降水、冬春季降雪的联系.结果表明:青藏高原地区大气中的云水有着显著的季节变化与水平分布差异;青藏高原春夏季总云量、高云云量高于秋冬季,CWP、COT与总云量的分布特征具有较好的一致性.高原云量高值区位于喀喇昆仑山与高原东南部;可可西里地区由于羌塘高压的下沉作用为云量低值区.青藏高原总云量在1984-2009年间呈现减少趋势;而CWP在高原总体以增加为主,但在各区域上的变化不一致,高原东部CWP增加而西部出现较弱的减小,这与来自孟加拉湾的水汽输送增加有关.青藏高原中东部地区夏秋季降水受云量减少影响较小而与CWP的增加相一致呈增长趋势;该地区冬春季降雪略有减少,与总云量的年际变化具有正相关.  相似文献   

鄂尔多斯盆地晚三叠世延长期古湖盆生物相带划分及地质意义     

杨华  傅强  齐亚林  周新平  龚宁  黄少雄 《沉积学报》2016,34(4):688-693

鄂尔多斯盆地晚三叠世发育大型坳陷型湖盆。湖水的升降影响着湖盆水体面积的大小、深浅以及沉积体系发育分布,进而影响全盆地晚三叠延长统地层生储盖组合的发育特征。通过野外剖面、钻井岩芯中古生物化石的鉴定,结合古生物组合特征对鄂尔多斯盆地晚三叠世湖盆的古生物生态环境进行了恢复。确定鄂尔多斯晚三叠世湖盆是一个最大水深不超过60 m的浅水湖盆,属于温暖潮湿的淡水-半咸水环境。从湖岸到湖心,可以划分为预测古水深1～2 m的河流-沼泽生物相带;预测古水深3～15 m的滨岸-河口三角洲生物相带;预测古水深15～35 m的浅湖生物相带;预测古水深在35～60 m范围的半-深湖生物相带。这些生物相带的划分,为恢复鄂尔多斯盆地晚三叠世时期的岩相古地理奠定了基础,为盆地延长组沉积边界、盆地内沉积体系发育展布以及沉积相带的划分提供了坚实的地质依据,具有理论与实际意义。  相似文献   

板桥-合水地区长6₃储层成岩相孔隙结构特征及优质储层分布     

张茜  孙卫  明红霞  王倩  张龙龙 《沉积学报》2016,34(2):336-345

利用铸体薄片、扫描电镜、常规压汞、恒速压汞及相渗等资料,研究了板桥-合水地区长6₃储层成岩相类型及其微观孔隙结构特征,总结了不同成岩相的测井响应特征,确定了纵向及平面分布规律。结果表明优质成岩相的展布受沉积相、成岩作用与孔隙结构共同控制,尤其是喉道分布才是控制砂岩储层渗透性的主要因素。水云母胶结-残余粒间孔相和水云母胶结-长石溶蚀相储层主要分布于半深湖相重力流复合水道浊流沉积中,细-微细喉道发育,孔喉连通性好,渗流能力最好,油水呈相对均匀的渗流,孔隙内的油气极易通过喉道被开采出来;绿泥石胶结相、水云母胶结弱溶蚀相储层位于分支水道边缘,呈孤岛状分布,孔喉半径小但分布均匀,渗流能力中等-差;碳酸盐胶结相、碳酸盐+水云母胶结相储层主要发育在分支水道间,孔隙结构发育程度差,喉道细小且孔喉连通性差,富集于孔隙中的油气难以通过小喉道,采收率低。  相似文献   

The genus Perissocytheridea Stephenson, 1938 (Crustacea: Ostracoda) and evidence of brackish water facies along the Oligo-Miocene,Pirabas Formation,eastern Amazonia,Brazil     

《Journal of South American Earth Sciences》2016

Perissocytheridea Stephenson is characteristic of brackish water facies. In 57 samples from the Upper Oligocene to Lower Miocene, from five localities, Pirabas Formation, Pará State, Brazil eleven species have been identified. Among these species, four are new reports: Perissocytheridea punctoreticulata n. sp., Perissocytheridea largulateralis n. sp., Perissocytheridea colini n. sp. and Perissocytheridea pirabensis n. sp.; five species in open nomenclature: Perissocytheridea sp. 1, P. sp. 2, P. sp. 3, P. sp. 4, and P. sp. 5 and two species left in “aff.” abbreviation: Perissocytheridea aff. Perissocytheridea pumila and Perissocytheridea aff. Perissocytheridea brachyforma subsp. excavata. The distributional pattern of the Perissocytheridea combined with the occurrence of foraminifera Elphidium and Ammonia in the studied sections supports the presence of the brackish water facies to the respective layers. Their quantitative variation through the studied sections indicate more than one phase of salinity reduction (about >5 and <30 ppm) and/or the decrease of the sea level, forming lagoon along the Pirabas Formation. This genus has a wide paleobiogeographical occurrence and stratigraphic distribution ranging from the Cretaceous to Recent, and already been recorded in the northern of South America, especially in the Neogene of Solimões Basin, but this is the first report of a neotropical genus to the Oligo-Miocene deposits of Pirabas Formation, northern Brazilian Coast, Pará State.  相似文献   

Hydrogen sulfide measurements in air by passive/diffusive samplers and high-frequency analyzer: A critical comparison     

《Applied Geochemistry》2016

In this study, hydrogen sulfide (H₂S) measurements in air carried out using (a) passive/diffusive samplers (Radiello^® traps) and (b) a high-frequency (60 s) real-time analyzer (Thermo^® 450i) were compared in order to evaluate advantages and limitations of the two techniques. Four different sites in urban environments (Florence, Italy) and two volcanic areas characterized by intense degassing of H₂S-rich fluids (Campi Flegrei and Vulcano Island, Italy) were selected for such measurements. The concentrations of H₂S generally varied over 5 orders of magnitude (from 10⁻¹–10³ μg/m³), the H₂S values measured with the Radiello^® traps (H₂S_R) being significantly higher than the average values measured by the Thermo^® 450i during the trap exposure (H₂S_Ta), especially when H₂S was <30 μg/m³. To test the reproducibility of the Radiello^® traps, 8 passive/diffusive samplers were contemporaneously deployed within an 0.2 m² area in an H₂S-contaminated site at Mt. Amiata (Tuscany, Italy), revealing that the precision of the H₂S_R values was ±49%. This large uncertainty, whose cause was not recognizable, is to be added to that related to the environmental conditions (wind speed and direction, humidity, temperature), which are known to strongly affect passive measurements. The Thermo^® 450i analyzer measurements highlighted the occurrence of short-term temporal variations of the H₂S concentrations, with peak values (up to 5732 μg/m³) potentially harmful to the human health. The Radiello^® traps were not able to detect such temporal variability due to their large exposure time. The disagreement between the H₂S_R and H₂S_Ta values poses severe concerns for the selection of an appropriate methodological approach aimed to provide an accurate measurement of this highly toxic air pollutant in compliance with the WHO air quality guidelines. Although passive samplers may offer the opportunity to carry out low-cost preliminary surveys, the use of the high-frequency H₂S analyzer is preferred when an accurate assessment of air quality is required. In fact, the latter provides precise real-time measurements for a reliable estimation of the effective exposure to hazardous H₂S concentrations, giving insights into the mechanisms regulating the dispersion of this air pollutant in relation to the meteorological parameters.  相似文献   

Depositional System of the Carboniferous Huanglong Formation, Eastern Sichuan Basin: Constraints from Sedimentology and Geochemistry     

WANG Kun  HU Suyun  LI Wei  LIU Wei  HUANG Qingyu  MA Kui  SHI Shuyuan 《《地质学报》英文版》2016,90(5):1795-1808

Using analyses of the lithology, sequences, paleoenvironment, and tectonic setting, the depositional system of the Carboniferous Huanglong Formation in the eastern Sichuan Basin was identified. The lithological characteristics of the Lower Member, Middle Member, and Upper Member were analyzed and classified. Before the use of carbon, oxygen, and strontium isotopes in the analysis, all of the geochemical data were tested for validity. On the basis of the Z values obtained from carbon and oxygen isotopes, the paleoenvironments of the three members were elucidated. Lower Member was dominantly an enclosed marine environment with intense evaporation and little freshwater input into the sea. Middle Member developed in a semi-enclosed to normal marine environment with many rivers. Upper Member was formed in a normal marine environment. The east Sichuan Basin was enclosed by paleouplifts before the deposition of the Huanglong Formation, forming a relatively enclosed depositional setting. Paleogullies developed in the Silurian strata that underlie the Carboniferous rocks; these paleogullies can be identified. On the basis of a comprehensive analysis, we propose that the Huanglong Formation developed in a platform system. Four microfacies were identified: supratidal flat, dolostone flat, grain shoal, and shelf microfacies. The high-permeability and high-porosity characteristics of the grain shoal microfacies are favorable for hydrocarbon accumulation, while the supratidal flat and shelf microfacies developed very few high-quality reservoirs. The paleogullies, in which increased amounts of grain shoal microfacies developed, controlled the distribution of high-quality reservoirs.  相似文献   

天津市地热资源开发利用特征及存在问题分析          下载免费PDF全文

林溦  于彦  秦莉红  康楠 《地质找矿论丛》2016,31(4):592-599

天津地区的地热地质条件良好,蕴藏着丰富的地热资源。在地热资源的开发利用过程中,每年可产生可观的经济、社会和环境效益,但由于开发方式的不尽合理,带来诸多问题。文章阐述了天津开发利用地热资源的特征,分析了存在的问题。认为不同热储层间水力联系的存在和地热井间距的过小,造成开采层间相互影响较大;地热井布局不合理、开采层位相对集中、回灌程度不高导致局部热储层压力大幅度下降,持续的大幅度压力下降将引发吊泵和地面沉降;超标准排放地热尾水会造成资源浪费和热污染;采、灌井间距的过小和相对位置的不合理,存在冷突破风险。针对不同问题,给出了针对性解决问题的建议。  相似文献